Dysregulated Expression of Long Intergenic Non-coding RNAs (LincRNAs) in Urothelial Bladder Carcinoma

Long intergenic non-coding RNA (lincRNA) has been introduced as key regulators of diverse biological processes, including transcription, chromatin organization, cell growth and tumorigenesis. With regard to the potential role of lincRNAs in cancer development, one may postulate that differential expression of lincRNAs could be employed as a tool in cancer diagnosis, prognosis, and targeted therapy. In this study, we aimed to explore the putative correlation between the expression levels of two lincRNAs: LINC00152 and LINC01082 in the bladder cancer (BC), in comparison with its adjacent non-cancerous tissue. Fifty Iranian subjects diagnosed with BC, representing in different stages and grades participated in this study The mRNA expression levels of the abovementioned lincRNAs were comparatively analyzed in cancerous and their adjacent non-cancerous counterpart tissues, of each subject by Real-Time PCR. The expression levels of LINC00152, and LINC01082 were significantly lower in tumor tissues in comparison with their adjacent normal tissues (P<0.001). More notably, in the case of LINC01082 the reduced expression was differentiated by the muscle invasiveness pattern of the tumor (P= 0.05). Our study presents a new finding about the tumor suppressor potentiality of these lincRNAs in BC development that in turn may suggest them as candidate biomarkers. Replicating this study in higher number of BC subjects, coupled with functional analysis, is necessary to investigate interconnections between these RNAs and cancer development, leading to better understanding of cancer biology.

and also introducing potential markers for early diagnosis and prognosis, is very crucial in patient care.
Recent investigations using high throughput technologies such as whole-genome and RNA sequencing have identified a comprehensive prospect of molecular signatures (4). Large-scale sequencing revealed a great number of noncoding RNAs, comprising small/short and long noncoding RNAs. It is estimated that nearly 98% of transcribed regions composed of noncoding RNAs.
They contribute to a variety of biological functions, protect genomes from foreign nucleic acids, and can conduct DNA synthesis or genome rearrangement (5). Long non-coding RNAs They can be nuclear or cytoplasmic or both, and participate in gene regulation at the transcriptional or post-transcriptional levels, and are also actively involved in cell proliferation, differentiation, and apoptosis (6)(7)(8). Recently it has been demonstrated that lncRNAs interact with chromatin at more than thousands diver locations across multiple chromosomes, and modulate large-scale gene expression programs (9). LncRNAs biology has attracted a great attention in cancer genome research. There are evidences showing their roles in the pathophysiology of diseases, and also in the development and progression of human cancers.
They have the potential to be used as a marker for early diagnosis, and molecular targeted therapy.
Thousands of lncRNAs have been identified (10,11). A microarray analysis of the lncRNAs expression profile in BC detected 1,122 differentially expressed lncRNAs; among these, 734 lncRNAs were upregulated and 388 were downregulated (12). Genetically, lncRNAs are classified into sense, antisense, bidirectional, intronic, and intergenic. There are some reports that indicate lncRNAs play an oncogenic role in BC (10)(11)(12)(13)(14). Long intergenic noncoding RNAs (LincRNAs) are transcribed from non-coding DNA sequences between coding genes and do not overlap exons and other transcripts. LincRNAs that are localized in nucleus are involved in regulating gene transcription, and chromatin organization (9). In primary tumors and metastases, they show distinct gene expression patterns. Also, lincRNAs may affect human diseases and epigenetic information, the latter may affect cellular growth (15). There are over 5,000 lincRNAs that were annotated across human tissues using high-throughput sequencing technologies (16), but a small portion of them have been characterized. Despite the fact that lincRNAs are being considered as key regulators of different cellular processes, molecular mechanisms of action and the function of individual lincRNAs stay a challenge. It is reported that differences in expression of lincRNAs between normal and cancer cells are associated with cancer progression (15). Therefore, differential expression of lincRNAs can be useful for cancer diagnosis, prognosis and targeted therapy. LINC01082 is thought to be involved in long-range control of chromatin structure, and gene expression (17). It is reported that LINC00152 which is a new lincRNA, may participate in cell cycle arrest, apoptosis, epithelial to mesenchymal transition, cell migration, and may be used as a reliable biomarker for some cancer types diagnosis (18,19). Relatively, in colon cancer tissues, LINC 00152 increased expression is associated with poor prognosis, and in gastric cancer is correlated with invasion, lymph node metastasis and poor survival (20,21). Decreased expression of LINC 00152 has been observed in colorectal cancer (CRC) tissue and CRC cell line (22).

RNA Extraction and cDNA synthesis
Total RNA from tumor and adjacent non-  Table 1.  Table 2.

Expression analysis of lncRNAs
The relative gene expression level of      and LINC01082 (P= 0.032).

Discussion
This is the first study that addressed LINC00152 and LINC01082 expression levels in Iranian BC patients. We described dysregulation of these lincRNAs expression in tumoral tissues in comparison with non-tumoral tissues. Our results represent a correlation between some of clinicopathological parameters and these lncRNAs.
Although lincRNAs tend to have low expression levels, and have tissue specific or cell specific feature, but they are involved in cancer pathogenesis as oncogene or tumor suppressor and it is suggested that they can act as key regulators of diverse biological processes (23,24). They could govern cellular functions in different occasions from embryonic stem cell division to progression of cancer (24,25).
In the present study, the expression level of

Conflict of interest
The authors declare that there is no conflict of interest in this study.